The contractor shall maintain a colony of fifty-one (51) chimpanzees to be utilized in non-destructive experiments judged most likely to advance hepatitis or acquired immunodeficiency syndrome (AIDS) research. A major emphasis of research will be on hepatitis C virus (HCV) since this form of liver disease is responsible for over 90 percent of transfusion-transmitted hepatitis cases in the United States. Since the chimpanzee is the only animal susceptible to this human disease, the NHLBI colony may be used in research to characterize the virus and in efforts to develop an HCV vaccine. Another major focus will be on acquired immunodeficiency syndrome (AIDS) research. The causative agent, human immunodeficiency virus (HIV), can be readily transmitted from humans to chimpanzees. Therefore, this animal is an invaluable resource for testing the safety and efficacy of therapeutic agents as well as candidate AIDS vaccines. As the only animal model for HIV, the chimpanzee may also be exceedingly useful in studies of the pathogenicity and natural history of this virus.